The present invention relates to a split torque gearbox, and more particularly to a main gearbox for a rotary wing aircraft which directs significant power to a tail mounted pusher prop system.
A gearbox system of a rotary wing aircraft transfers power from a turbine engine to the rotor system. A typical system may direct power from several turbine engines to a single rotor system which may include a multiple of blades. Since the rotational velocity of the rotor is significantly lower than the rotational velocity of the turbine engines, the turbine engine rotational velocity must be reduced by the gearbox system. In reducing the rotational velocity of the turbine engine output, torque is increased through a series of intermediate gear stages and shafts, before the final output drive is provided to the rotor.
Conventional rotary-wing aircraft have a forward airspeed limited by a number of factors. Among these is the tendency of the retreating blade to stall at high forward airspeeds. As the forward airspeed increases, the airflow velocity across the retreating blade slows such that the blade may approach a stall condition. In contrast, the airflow velocity across the advancing blade increases with increasing forward speed.
Recent designs have pursued high speed compound aircraft in which a secondary translational propulsion system provides translational thrust while the main rotor system is operated in a reverse airflow condition during a high speed flight profile. Although such concepts have proven effective, the main planetary gearboxes for such aircraft are quite complicated and have heretofore resulted in gearbox systems which may be relatively heavy in weight and of significant packaging volume. As the rotor system locates the gearbox in an airframe center section, such a weighty and voluminous gearbox system often extends into the aircraft cabin section which may reduce aircraft payload and cabin space to an impractical capacity.
Accordingly, it is desirable to provide a lightweight, low profile gearbox system for a high speed compound rotary-wing aircraft that is readily mountable to an airframe above an aircraft cabin so as to increase payload and cabin space.